1. Field of the Invention
The present invention relates to power tools having lights and methods for operating such power tools. More particularly, the present invention relates to power tools having lights that can light a work area and are more convenient to use than known power tools.
2. Description of the Related Art
Known power tools having lighting devices generally provide a light that operates separately from the tool. That is, the lighting circuit is electrically separate from the motor operation circuit and thus, the light can be turned on even when the tool is not being used. Thus, if the power tool is powered by rechargeable batteries and the light is left on when the power tool is not being used, the rechargeable batteries may be completely discharged and possibly permanently damaged.
FIG. 9 shows a circuit taught by German Patent No. DE 3831344 C2 to control the operation of a light 34 for another type of power tool, in which the lighting circuit and the motor 18 can be operated by a single switch. This known power tool has a switch 76 that can be pushed by the user to activate the motor 18 and the same switch 76 also can control the light. Specifically, according to this German reference, switch 76 is a two-stage push switch. If the switch 76 is pushed to an intermediate position, the lighting contact S1 will close (on state) and the light 34 will turn on. The motor contact S2 is open (off state), such that the motor 18 does not operate while the switch 76 is in the intermediate position. Therefore, the user can utilize the light in a manner similar to a flashlight in order to position the power tool with respect to the work piece (i.e., a board) while the motor 18 is stopped.
If the two-stage switch 76 is pushed further, the motor contact S2 will close (on state) and thus, the motor 18 will begin to rotate. As a result, the user can begin performing the intended power tool operation, such as driving a screw using a powered screwdriver.
A timer circuit 102 is provided to turn off the light 34 after a predetermined period of time. Thus, the user is not required to manually turn off the light. This timer circuit 102 starts the timing operation when the motor contact S2 closes (i.e. beginning of the motor on state) and opens (i.e. disconnects) the second lighting contact K1 after the predetermined period of time has passed, thereby turning off the light 34. German Patent No. DE 3831344 C2 also describes another design in which the timer circuit 102 starts the timing operation when the lighting contact S1 is closed (turned on). Thus, the light 34 can be turned off either (1) after a pre-determined period of time has passed since the motor 18 began to rotate or (2) after a pre-determined period of time has passed since the light 34 was turned on. As a result, the light 34 will automatically turn off and the user is not required to manually turn off the light 34.
In this known power tool, the switch 76 must be pressed to the intermediate position in order to maintain the light 34 in the on state. Therefore, the operator must adjust the position of the power tool and/or workpiece while holding the switch 76 in the intermediate position. In other words, the user can not remove his/her finger from the switch while adjusting the position and angle of the power tool and/or work. Therefore, the user's hand may become fatigued if repeated screw-driving operations are required.
If the stroke length of the switch 76 is long, it may be easier to hold the switch in an intermediate position in order to turn on the light 34 while preventing the motor 18 from unintentionally starting. However, the user must move his or her finger over a longer range of motion during the lighting and screw-driving operations, thereby causing fatigue. On the other hand, if the stroke length of the switch 76 is short, it may be easier to start the power tool operation, but it may become more difficult to hold the switch in the intermediate position in order to light the work area before being the power tool operation.
Furthermore, the known power tool requires a two-stage push-type switching device and cannot use a common, inexpensive single stage on-off switching device, thereby raising manufacturing costs.